The present invention generally relates to the use of fiber optics in wellbores. More particularly, this invention relates to the use of fiber optics in deviated wells, including horizontal wells. The present invention may also be used in conjunction with pipelines, such as but not limited to subsea pipelines.
Flow of fluids into and along a deviated well is highly dynamic and is difficult to analyze. Among other flow regimes, fluid flow along a deviated well can be stratified, wherein different fluids stratify based on their density and flow along the well within their stratum. Typically, fluids stratify so that hydrocarbon gas is located on top, hydrocarbon liquid underneath the hydrocarbon gas, and water, if any, below the hydrocarbon liquid. Another flow regime that may be present in a deviated well is “slug flow,” wherein slugs of gas and liquid alternately flow along the well.
In any case, not only is the identity of the fluids (hydrocarbon gas, hydrocarbon liquid, water, or a mixture thereof) along the length and vertical axis of the deviated well difficult to determine, but the location of any hydrocarbon gas/hydrocarbon liquid/water interface(s) (if such is present) is also difficult to establish. This information would be useful to an operator in order to understand the content and fluid contributions of the relevant formation and wellbore. With such information, an operator could diagnose inflow characteristics and non-conformances, with a view to optimizing production conditions or planning interventions for remediations.
Similarly, many pipelines, such as subsea pipelines, also include stratified flow. In these pipelines, it would also be useful to identify the fluids flowing therethrough and the presence and location of any stratification.
Thus, there exists a continuing need for an arrangement and/or technique that addresses one or more of the problems that are stated above.